The present invention relates to a tubular pipe element comprising a rigid longitudinal part and a flexible longitudinal part.
Such elements are known, for example, that form tubular junction elements between two thermoplastic pipes or between a thermoplastic pipe and a nipple. Such an element is intended, for example, to be installed in the fuel feed circuit of a motor vehicle to connect the nipple of the tank to the pipe which is connected to the system for injecting fuel into the combustion chambers of the engine.
In such an application, the pipe element joining the thermoplastic pipe to the tank nipple must provide a leakproof junction that withstands being torn apart while nevertheless being relatively flexible to ensure that the vibration forces to which the junction is subjected while the vehicle is in operation do not give rise to leaks or to the junction breaking. In addition, in the motor industry, assembly rates are high and the nipple must therefore be connected to the pipe quickly and without requiring tooling that is difficult to implement.
In order to satisfy these requirements, it is known to interpose a flexible part comprising an elastomer sleeve between the nipple and the pipe. To do this, a rigid part constituted by an endpiece comprising a first male part with serrated tangs and a second male part axially in line therewith and in the form of a nipple is previously mounted on the pipe by inserting the male part having serrated tangs into one end of the pipe. Because of the forces involved, that operation cannot be performed manually and it is implemented by means of tooling dedicated to that purpose. The nipple-shaped male part is then engaged in one end of the flexible sleeve and a metal collar is placed around the flexible sleeve to clamp it onto the nipple-shaped male part. The pipe fitted in this way can then be mounted on a vehicle on an assembly line and can be connected to the nipple of the tank or to some other element of the vehicle. This operation is performed manually by an operator who engages the free end of the flexible sleeve on the tank nipple and then clamps it onto the nipple by means of a clamping collar. The junction made in this way satisfies the above-mentioned requirements in satisfactory manner. However, the structure of that junction is complex and requires a relatively large number of pieces (four pieces: a rigid endpiece; a flexible sleeve; and two clamping collars). This gives rise to expensive assembly operations and complicates stock management. In addition, the minimum length of the junction corresponds substantially to the length of the flexible sleeve, i.e. to the sum of the length of the tank nipple plus the length of the endpiece nipple plus the distance between the tank nipple and the endpiece nipple. This length makes it difficult to install the junction in vehicles where the space available for components is becoming smaller and smaller. In addition, the junction is relatively heavy, which goes against the present trend in the motor industry where manufacturers are seeking to reduce vehicle weight so as to limit fuel consumption.
The invention provides a pipe element possessing a longitudinal axis along which there extend in succession a rigid tubular part and a flexible tubular part constituting a single piece, the rigid part having one end presenting a substantially radial surface for connection to an end portion of the flexible part and, at the radial connection surface, means for defining an additional surface for connection to the end portion of the flexible part, at least a part of the additional connection surface extending substantially parallel to the longitudinal axis.
The means for defining an additional connection surface enable the connection between the rigid part and the flexible part to be reinforced both against pull-off forces parallel to the longitudinal axis and against transverse forces in bending, the ability to withstand these forces being improved in particular by the part of the additional connection surface that extends substantially parallel to the longitudinal axis of the pipe element. The pipe element is also simple in structure, compact, and relatively lightweight. In addition, the pipe element can be made by two-material injection so it is inexpensive.
In a first embodiment of the invention, the means for defining the additional connection surface comprise a ring disposed coaxially about the longitudinal axis of the element and embedded at least in part in the end portion of the flexible part, the ring having a free edge optionally presenting a step projecting radially into the end portion of the flexible part. The rigid part is thus simple in structure and the connection between the rigid part and the flexible part is particularly strong in withstanding transverse forces.
In a second embodiment, the means for defining an additional connection surface comprise tongues extending substantially parallel to the longitudinal axis of the pipe element, the tongues being embedded in the end portion of the flexible part and reinforcing said flexible part in a radial direction. The tongues thus serve to increase the strength of the flexible part against the pressure of the fluid flowing in the circuit in which the pipe element is installed, while nevertheless conserving sufficient flexibility for the flexible part.
In a particular application, the pipe element forms a tubular junction element for joining a thermoplastic pipe to a nipple, the rigid part having a male portion provided with external ridges for insertion into the pipe and a shoulder secured to said end of the rigid part and presenting on its side opposite from the male portion a surface that forms the radial connection surface for connection to the end portion of the flexible part, the flexible part being constituted by a flexible sleeve for receiving the nipple via its end opposite from the rigid part. It is thus possible to limit the number of pieces needed for joining a pipe to a nipple, with this number being limited to a tubular junction element plus optionally a clamping collar enabling the nipple to be fixed in the flexible sleeve. The weight of the junction made in this way is likewise small. The length of the junction then corresponds to the length of the nipple plus the distance between the nipple and the rigid part of the tubular junction element. The junction is thus relatively short.
According to a particular characteristic, the flexible sleeve presents at least one mark in relief on its outside for positioning a clamping collar, which mark is constituted, for example, by a groove or an annular bead. The positioning mark enables the operator assembling the flexible sleeve on the nipple to place the clamping collar accurately on the portion of the sleeve that extends around the nipple.